First three‐dimensional simulation of the Perkins instability in the nighttime midlatitude ionosphere

A three‐dimensional numerical simulation in the nighttime midlatitude ionosphere is developed for the first time and applied to the Perkins instability in the midlatitude F region. Growth of the Perkins instability is successfully reproduced under nighttime condition, and the numerical results basically agree with a linear theory and previous two‐dimensional numerical studies. Northwest‐southeast (NW‐SE) alignment of density perturbations is generated from random seeding by applying a southeastward neutral wind. The perturbations are dominant at altitudes of 200–300 km where a steep density gradient exists, which is consistent with the altitude of 630‐nm airglow emission that often shows NW‐SE alignment. Further simulation in terms of the E‐F coupling can be done in the near future.